The main objective of the application is to create the infrastructure necessary for the development of the Puerto Rican Neonatal Twin Registry (PRNTR). The initial development of this registry involves three main activities: 1) the establishment of a computerized data base that will record basic demographic, health and family history data of all twins born in the island from January 1, 2000 to December 31, 2001; 2) the development of a computerized tracking system for the long term follow up of twins and 3) the organization of two (one per year) that will familiarize faculty and students on the development and maintenance of twin registries and that will provide introductory material on genetic research methods. The successful completion of this initial phase of the development of the PRNTR will place the University of Puerto Rico's Medical Sciences Campus in a strong position to attract funding from federal and private sources through competitive mechanisms to study the genetics of specific illnesses. It is our ultimate goal to develop this invaluable national registry of Latino twin families as a means of addressing a series of unanswered questions involving cross-cultural comparisons, genetic and etiologic heterogeneity, and possible family cultural protective factors. This line is expected to facilitate improved treatment and prevention for common complex conditions in humans. The development of this national twin registry benefits from several very unique and synergistic factors. First, the team of investigators from the Virginia Commonwealth University, who will be co-investigators in this application, are renowned for mor than 20 years of experience in the areas of statistical genetic analysis and the development and prospective maintenance of large, population-based twin registries such as that proposed here. Second, the team of investigators from the University of Puerto Rico has an impressive track record of cutting edge epidemiological investigations of psychosocial and environmental factors in mental health and the longitudinal tracking of Latino populations together with vast experience in neonatal clinical research. Finally, the proposed study has the unique advantage of having obtained the full cooperation of the Director of the Demographic Registry of Puerto Rico. Data from birth certificates of twins will be made available electronically within 24 hours of receipt at the central office of the registry. Information collected at the Demographic Registry on twins will be transferred to a data base developed in conjunction with VCU for the PRNTR. After the initial data is obtained, families will be contacted by letter and phone in order to obtain important tracking information as well as information about zygosity, family and child health history, family structure, twins' emotions and temperament. A Computer-Aided Telephone Interview (CATI) program, will be developed and piloted in the first six months of the first year and will be used to gather basic recruitment information from non-respondents to the mail survey. A series of strategies that have been successfully used by the investigators of the VCU Mid Atlantic Twin Registry will be used for the long-term maintenance of contact and cooperation with study participants. It is hoped that one the basic infrastructure of the PRNTR is established, that funding will be obtained through either foundations or NIH to continue collecting the basic information needed for the Registry to be maintained.